This invention relates to electrical adapters, and more particularly to improved 3-wire, grounding type adapter with an on/off switch and a locking mechanism.
The hazard of operating ungrounded electrical devices is well recognized. As a result, the Underwriter""s Laboratories, Inc. and many electrical codes long have required that all portable electrical tools be equipped with suitable grounding means.
The xe2x80x9cUnderwriter""sxe2x80x9d have required that plugs for electrical devices be equipped with a three-prong plug for insertion into a 3-wire receptacle.
Over the years, a variety of three-prong plugs have been patented, see U.S. Pat. Nos. 2,323,736; 2,922,134; 2,986,718; 2,876,426; 3,134,631; 3,178,667; 3,219,962; and 2,984,808.
As disclosed in U.S. Pat. No. 2,323,736, there is shown a three-prong plug in which the ground prong is capable of being retracted from a position of use, depending on whether or not a 3-wire electrical outlet is encountered.
When retracted for use with a 2-wire outlet, however, this leaves the electrical device with which the plug is associated ungrounded. U.S. Pat. No. 2,984,808 discloses another three-prong convertible plug in which the ground plug can be pivoted into the use position or not as desired. A xe2x80x9cpig-tailxe2x80x9d connection is provided on the plug, and in connection with the ground, for connection to the ground screw of a 2-wire receptacle. Another three-prong plug in which a pivotable ground prong is provided is disclosed in U.S. Pat. No. 2,986,718. A xe2x80x9cpig-tailxe2x80x9d is provided which connects to the ground and which is provided with a connection at the other end for connection to the ground screw in case of use with a 2-wire electrical outlet.
U.S. Pat. Nos. 2,876,426 and 2,922,134 disclose electrical connecting plugs in which a pivotable grounding element is provided. The ground prong on encountering the 2-wire outlet is pivoted so that the finger portion of the grounding prong is out of position so that the connecting plug can be used. In U.S. Pat. No. 2,876,426, the other end of the pivoted prong is constructed so that on the prong being pivoted, it is in contact with the grounded receptacle plate and, in turn, grounds the electrical device.
U.S. Pat. No. 3,134,631 discloses another three-prong electrical plug in which the ground prong is pivotable out of position in case the plug is used with a 2-wire electrical outlet. The ground prong is provided with a groove adjacent its free end for insertion of a ground wire which in turn can be connected to a ground lead in the electrical outlet. A further electrical plug which is provided a pivotable prong is disclosed in U.S. Pat. No. 3,178,667. When a 2-wire outlet is encountered, the pivotable ground prong therein is resiliently urged against the faceplate of the receptacle to establish a ground, thereby reducing the possibility of a shock being transmitted to the user of an electrical device.
U.S. Pat. No. 3,219,962 discloses an electrical connector plug in which a pivotable ground prong is provided and which is disclosed for use with either a 2 or 3-wire receptacle. The ground plug is biased to its operative position.
Note also U.S. Pat. No. 5,171,155, which teaches the use of safety locks for electrical appliances.
While all of the electrical plugs as above disclosed are suitable to a degree, their use does involve certain problems and disadvantages. None of the referenced adapters uses a switch with a 3-prong grounding plug and a security screw for attaching a plug of an electric cord to a power on/off switching device.
A three-wire grounding electric adapter comprising:
(a) a body comprising a first end and a second end wherein the first end has a vertical planar face capable of detachably engaging a 3-wire electric cord, and the second end has a second vertical planar face;
(b) a switch mounted on the body for permitting the adapter to complete or disrupt positive electrical current from electrical receptacle to an electric device;
(c) at least two electric contact blades fixedly mounted in the second end and extending outwardly from the second vertical planar face for engaging in an electric outlet; and
(d) a security screw for securing at least one blade of an electric device plug into the adapter locking at least one blade into the adapter.